JP4136755B2 - PTC thermistor made of ternary alloy material - Google Patents
PTC thermistor made of ternary alloy material Download PDFInfo
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- JP4136755B2 JP4136755B2 JP2003092278A JP2003092278A JP4136755B2 JP 4136755 B2 JP4136755 B2 JP 4136755B2 JP 2003092278 A JP2003092278 A JP 2003092278A JP 2003092278 A JP2003092278 A JP 2003092278A JP 4136755 B2 JP4136755 B2 JP 4136755B2
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- temperature
- resistance
- alloy material
- resistance value
- ternary alloy
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Description
【0001】
【発明の属する技術分野】
この発明は、3元合金材料からなる正温度係数(PTC)サーミスタに関する。
【0002】
【従来の技術】
電子部品の高集積、高精度の要求から回路の動作時の温度検出、回路の温度変化による特性の変化を補償するための感温素子が求められている。電気素子の温度特性とこれを補償するために用いるサーミスタの温度特性とは、互いに正負のみ反転したものが理想的であるが、電気素子によりその特性は異なる。そこで、これを整合させるためのソフトウェアや回路が設けられる。この場合、サーミスタの特性としては、非線形な曲線より直線に近い方が整合させやすい。
【0003】
温度を抵抗値の変化として検知する素子材料のうち正の温度係数をもつものとしては、白金、あるいはルテニウム、ロジウムなど白金以外の金属、あるいはチタン酸バリウムなどの複合金属酸化物などがある。このうち白金は安定した抵抗温度特性を有し、ルテニウムやロジウムは白金に比べ安価であり、チタン酸バリウムは設定温度(キューリー温度)で高い感度(抵抗変化率)を有するなど、各々異なる特徴がある。
【0004】
【発明が解決しようとする課題】
しかし、白金は、非常に高価であり、また純金属であることから実現できる抵抗値も低い。また、他の金属も実現できる抵抗値が低い点は同様であり、例えば市販されている某メーカーの感温抵抗素子ではサイズが1.6×0.8mmあるいは2.0×1.2mmで抵抗温度係数が1500ppm/℃のものの場合、抵抗値範囲が1k〜10kと狭く、且つ抵抗値が低い。また抵抗温度係数が2700ppm/℃のものとなると、抵抗値範囲が1k〜3kと更に狭い。他のメーカーの抵抗材料も同様である。感温抵抗素子が金属膜からなる場合、抵抗値は理論的に膜厚を薄くすることにより高められるが、電気伝導の連続性を保つには10nm程度が限界であり、あとは材質を変えるしかない。一方、チタン酸バリウムは、その抵抗温度特性が直線的でなく、電子部品の一般的な使用温度範囲で種々の温度を抵抗値の変化として検知する素子としては適していない。
【0005】
従って、これまで負の温度係数をもつ被補償素子・回路に対しての正温度係数、高抵抗値、直線性の良好な抵抗温度特性を合わせもった感温素子はない。
それ故、この発明の課題は、正温度係数、高抵抗値及び直線性の良好な抵抗温度特性を有する合金材料からなるサーミスタを提供することにある。
【0006】
【課題を解決するための手段】
その課題を解決するために、この発明のサーミスタを構成する合金材料は、
Al、Cr及びSiの3元素から構成され、Al:10〜84at%、Cr:9〜65at%及びSi:8〜58at%の組成範囲をもつことを特徴とする。
この組成範囲をもつことにより、高抵抗値で且つ直線性に優れた正の抵抗温度特性が得られる。従って、この合金材料からなるPTCサーミスタによれば、電気素子の特性と整合するプログラムや回路を容易に制作することができる。また、この合金材料からなる薄膜と、この薄膜を支持するガラス基板やセラミック基板などの絶縁基板とを備えることにより、直線性に優れた抵抗体素子として用いることもできる。
【0007】
【実施例】
アルミニウムAl基板上にクロムCrチップおよびケイ素Siチップを配置し、これをターゲットとしてスパッタリングすることにより、またはCr基板上にAlチップおよびSiチップを配置し、これをターゲットとしてスパッタリングすることにより、またはSi基板上にAlチップおよびCrチップを配置し、これをターゲットとしてスパッタリングすることによってアルミナセラミックの電気的絶縁基板上にAlCrSiからなる種々の組成の3元合金薄膜を約100nmの厚さで形成した。薄膜中の成分比は、Al(又はCr、Si)基板の重量に対するCr(又はAl、Si)チップ及びSi(又はAl、Cr)チップの重量で調整した。そのような薄膜に2%水素と98%窒素の還元性混合ガス雰囲気中で450℃〜600℃の温度範囲の熱処理を行ったのち、4端子法により25℃及び125℃における比抵抗を測定し、測定値から温度係数を算出した。
【0008】
ここで温度係数は以下の式(1)で定義される値である。
温度係数=(ρ−ρ0)/(ρ0ΔT)・・・・(1)
ρ:任意温度(本例では125℃)での比抵抗
ρ0:基準温度(本例では25℃)での比抵抗
ΔT:温度差
【0009】
例として560℃で熱処理した後の組成と比抵抗及び抵抗温度係数を表1に、また組成図を図1にそれぞれ示した。図中、四角枠内の数字は試料番号である。図1の破線で囲まれる組成が本発明合金材料に属し、表1からこの範囲において正温度係数としておよそ150〜3000ppm/℃の広い範囲で任意の温度係数の素子が得られることが判る。また対応する比抵抗は0.01〜1.25mΩ・cmであった。
【0010】
【表1】
【0011】
上記で得られた比抵抗に基づき、薄膜製造技術を用いて本発明の合金材料で実現できる感温抵抗体素子の抵抗値範囲を表2に示した。表中、素子サイズ1.6×0.8mmにおいて上段が試料番号10、中段が試料番号6、下段が試料番号2に対応する。素子サイズ2.0×1.2mmの場合も同様である。このように同じ素子サイズであっても本発明の薄膜を用いることで、はるかに広い抵抗値範囲、特に上限抵抗値が高く正温度係数を持った感温抵抗素子を実現することができる。
【0012】
【表2】
【0013】
次に、熱処理温度を変化させた場合の、いくつかの組成における温度係数の変化を図2に示す。このように、本発明合金材料によれば温度係数の値が組成により一義的に決まるのではなく、熱処理温度を制御することによりさらに精密に目的値に調整することが可能である。
次に、図3に上記試料のうち5点の抵抗温度特性を示す。また比較のために、図4に市販されている松下電器産業株式会社製の感温抵抗ERVシリーズのカタログに基づく抵抗温度特性を示した。図3と図4を対比して判るように、本発明の合金材料は市販品と同程度の良好な直線性を有していた。ちなみに、上記市販品は、抵抗値範囲の上限が10kΩにとどまっている。
【0014】
【発明の効果】
以上のようにこの発明による3元合金材料を用いることで、広い範囲の正温度係数をもち、抵抗値範囲が広く、特に上限抵抗値が高く、抵抗温度特性の直線性に優れた感温抵抗素子が実現可能となる。
【図面の簡単な説明】
【図1】3元合金材料の組成図である。
【図2】実施例の合金材料の熱処理温度と抵抗温度係数の関係を示すグラフである。
【図3】実施例の合金材料の抵抗温度特性を示すグラフである。
【図4】市販の感温抵抗の抵抗温度特性を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
This invention relates to positive temperature coefficient (PTC) thermistor comprising a ternary alloy.
[0002]
[Prior art]
Due to the demand for high integration and high accuracy of electronic components, there is a need for a temperature sensing element for detecting temperature during circuit operation and compensating for changes in characteristics due to temperature changes in the circuit. Ideally, the temperature characteristics of the electric element and the temperature characteristics of the thermistor used to compensate for the temperature characteristic are reversed only positive and negative, but the characteristics differ depending on the electric element. Therefore, software and a circuit for matching them are provided. In this case, as the thermistor characteristics, matching closer to a straight line is easier than a non-linear curve.
[0003]
Among element materials that detect temperature as a change in resistance value, materials having a positive temperature coefficient include platinum, metals other than platinum such as ruthenium and rhodium, and composite metal oxides such as barium titanate. Of these, platinum has stable resistance-temperature characteristics, ruthenium and rhodium are cheaper than platinum, and barium titanate has high sensitivity (resistance change rate) at a set temperature (Curie temperature). is there.
[0004]
[Problems to be solved by the invention]
However, platinum is very expensive and has a low resistance value because it is a pure metal. Moreover, the point that the resistance value which other metals can also implement | achieve is the same, for example, in the thermosensitive resistance element of the cocoon maker marketed, resistance is 1.6 * 0.8mm or 2.0 * 1.2mm. When the temperature coefficient is 1500 ppm / ° C., the resistance value range is as narrow as 1 k to 10 k and the resistance value is low. Further, when the resistance temperature coefficient is 2700 ppm / ° C., the resistance value range is further narrowed to 1 k to 3 k. The same applies to resistive materials from other manufacturers. When the temperature-sensitive resistance element is made of a metal film, the resistance value can be theoretically increased by reducing the film thickness. However, about 10 nm is the limit for maintaining the continuity of electric conduction, and the only change is the material. Absent. On the other hand, barium titanate has a non-linear resistance-temperature characteristic, and is not suitable as an element for detecting various temperatures as changes in resistance value in a general operating temperature range of electronic components.
[0005]
Therefore, there is no temperature-sensitive element having a resistance temperature characteristic with a positive temperature coefficient, a high resistance value, and a good linearity for a compensated element / circuit having a negative temperature coefficient.
Therefore, an object of the present invention is to provide a thermistor made of an alloy material having a positive temperature coefficient, a high resistance value, and a resistance temperature characteristic with good linearity.
[0006]
[Means for Solving the Problems]
In order to solve the problem, the alloy material constituting the thermistor of the present invention is:
It is composed of three elements of Al, Cr and Si, and has a composition range of Al: 10 to 84 at%, Cr: 9 to 65 at%, and Si: 8 to 58 at%.
By having this composition range, a positive resistance temperature characteristic having a high resistance value and excellent linearity can be obtained. Therefore, according to the PTC thermistor made of this alloy material, it is possible to easily produce programs and circuits that match the characteristics of the electric elements. Moreover, it can also be used as a resistive element excellent in linearity by providing the thin film which consists of this alloy material, and insulating substrates, such as the glass substrate and ceramic substrate which support this thin film.
[0007]
【Example】
By placing a chromium Cr chip and a silicon Si chip on an aluminum Al substrate and sputtering it as a target, or by placing an Al chip and a Si chip on a Cr substrate and sputtering this as a target, or Si An Al chip and a Cr chip were placed on the substrate, and sputtering was performed using this as a target to form ternary alloy thin films having various compositions of AlCrSi on an alumina ceramic electrically insulating substrate with a thickness of about 100 nm. The component ratio in the thin film was adjusted by the weight of the Cr (or Al, Si) chip and the Si (or Al, Cr) chip with respect to the weight of the Al (or Cr, Si) substrate. After such a thin film was heat-treated in a reducing gas mixture atmosphere of 2% hydrogen and 98% nitrogen in a temperature range of 450 ° C. to 600 ° C., the specific resistance at 25 ° C. and 125 ° C. was measured by the four-terminal method. The temperature coefficient was calculated from the measured values.
[0008]
Here, the temperature coefficient is a value defined by the following equation (1).
Temperature coefficient = (ρ−ρ 0 ) / (ρ 0 ΔT) (1)
ρ: specific resistance at an arbitrary temperature (125 ° C. in this example) ρ 0 : specific resistance at a reference temperature (25 ° C. in this example) ΔT: temperature difference
As an example, the composition, specific resistance and resistance temperature coefficient after heat treatment at 560 ° C. are shown in Table 1, and the composition diagram is shown in FIG. In the figure, the number in the square frame is the sample number. The composition surrounded by the broken line in FIG. 1 belongs to the alloy material of the present invention, and it can be seen from Table 1 that an element having an arbitrary temperature coefficient can be obtained in this range within a wide range of about 150 to 3000 ppm / ° C. as a positive temperature coefficient. The corresponding specific resistance was 0.01 to 1.25 mΩ · cm.
[0010]
[Table 1]
[0011]
Based on the specific resistance obtained above, Table 2 shows the resistance value range of the temperature sensitive resistor element that can be realized with the alloy material of the present invention using the thin film manufacturing technique. In the table, in the element size 1.6 × 0.8 mm, the upper stage corresponds to
[0012]
[Table 2]
[0013]
Next, FIG. 2 shows changes in temperature coefficients in several compositions when the heat treatment temperature is changed. Thus, according to the alloy material of the present invention, the value of the temperature coefficient is not uniquely determined by the composition, but can be adjusted to the target value more precisely by controlling the heat treatment temperature.
Next, FIG. 3 shows resistance temperature characteristics of five points of the sample. For comparison, FIG. 4 shows resistance temperature characteristics based on a catalog of commercially available temperature sensitive resistance ERV series manufactured by Matsushita Electric Industrial Co., Ltd. As can be seen by comparing FIG. 3 and FIG. 4, the alloy material of the present invention had good linearity comparable to that of a commercial product. Incidentally, the above-mentioned commercial product has the upper limit of the resistance value range of only 10 kΩ.
[0014]
【The invention's effect】
As described above, by using the ternary alloy material according to the present invention, a temperature sensitive resistor having a wide range of positive temperature coefficients, a wide resistance value range, a particularly high upper limit resistance value, and excellent resistance temperature characteristic linearity. An element can be realized.
[Brief description of the drawings]
FIG. 1 is a composition diagram of a ternary alloy material.
FIG. 2 is a graph showing a relationship between a heat treatment temperature and a resistance temperature coefficient of an alloy material of an example.
FIG. 3 is a graph showing resistance temperature characteristics of an alloy material of an example.
FIG. 4 is a graph showing a resistance temperature characteristic of a commercially available temperature sensitive resistor.
Claims (1)
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JP2003092278A JP4136755B2 (en) | 2003-03-28 | 2003-03-28 | PTC thermistor made of ternary alloy material |
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JP2003092278A JP4136755B2 (en) | 2003-03-28 | 2003-03-28 | PTC thermistor made of ternary alloy material |
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JP4136755B2 true JP4136755B2 (en) | 2008-08-20 |
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Families Citing this family (4)
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JP4742758B2 (en) * | 2005-09-06 | 2011-08-10 | 住友金属鉱山株式会社 | Thin film resistor and manufacturing method thereof |
JP5669016B2 (en) * | 2011-04-18 | 2015-02-12 | 三菱マテリアル株式会社 | Sputtering target and manufacturing method thereof |
JP6355022B2 (en) * | 2013-08-30 | 2018-07-11 | 三菱マテリアル株式会社 | Metal nitride material for thermistor, manufacturing method thereof, and film type thermistor sensor |
JP6354947B2 (en) * | 2013-08-30 | 2018-07-11 | 三菱マテリアル株式会社 | Metal nitride material for thermistor, manufacturing method thereof, and film type thermistor sensor |
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